Noto Peninsula Tsunami on May 5, 2023  


We have simulated the tsunami generated from the Noto Peninsula, Japan earthquake (37.540°N, 137.305°E, depth=8.7km, M=6.2 at 05:42:04 UTC according to USGS) on May 5, 2023 (Fig. 1).
The fault length and width are 20 km × 10 km. The average slip on the fault is 0.25 m. The seismic moment is 2.5 × 1018 Nm (Mw = 6.2) assuming the rigidity of 5 × 1010 N/m².

Case 1
The focal mechanism is strike: 219°, dip: 47°, slip: 81° from the USGS's W-phase moment tensor solution (NP1).
The top depth of the fault was assumed to 1 km.

Case 2
The focal mechanism is strike: 52°, dip: 44°, slip: 99° from the USGS's W-phase moment tensor solution (NP2).
The top depth of the fault was assumed to 1 km.

As the initial condition for tsunami, static deformation of the seafloor is calculated for a rectangular fault model [Okada, 1985] using the source model. For the tide gauges along the coast, we used the bathymetry data of J-EGG500 with 12 arc-second grid interval. To calculate tsunami propagation, the linear shallow-water, or long-wave, equations were numerically solved by using a finite-difference method [Satake, 1995]. We downloaded the tide gauge data from IOC's and GSI's web sites, respectively, and compared the simulated tsunami waveforms and the observed ones (Fig. 2). We can see the tsunami propagation in the Japan Sea (Fig. 3).


Fig.1 Tsunami Source Model Case1 Fig.1 Tsunami Source Model Case2

Fig.1 Tsunami Source Models (Case 1: left, Case 2: right)
The red lines indicate uplift with the contour interval of 0.01 m, while the blue dotted lines indicate subsidence with the contour interval of 0.01 m. The focal mechanism determined by USGS is also shown.


Fig.2 Maximum Height of Tsunami

Fig.2 Maximum Height of Simulated Tsunami and Tsunami Waveforms
Solid lines in red indicate the observed tsunami waveforms. The blue and purple lines are calculated tsunami waveforms for the Cases 1 and 2, respectively.


Fig.3 Tsunami propagation

Fig.3 Tsunami Propagation (Click to start animation)
The red color means that the water surface is higher than normal sea level, while the blue means lower.


by Yushiro Fujii (IISEE, BRI) and Kenji Satake (ERI, Univ. of Tokyo)
Okada, Y. (1985), Surface Deformation Due to Shear and Tensile Faults in a Half-Space, Bull. Seismol. Soc. Am., 75, 1135-1154.
Satake, K. (1995), Linear and Nonlinear Computations of the 1992 Nicaragua Earthquake Tsunami, Pure and Appl. Geophys., 144, 455-470.

Last Updated on 2023/5/6